High strength glass-ceramics having petalite and lithium silicate structures

ABSTRACT

In embodiments, a lithium-containing aluminosilicate glass-ceramic article includes a fracture toughness of 1 MPa·m 1/2  or greater; a ring-on-ring strength of at least 300 MPa; a compressive stress layer formed by ion-exchange having a depth of layer (DOL) of at least about 30 μm; and a transmittance of at least 85% for light in a wavelength range from 400 nm to 700 nm at a thickness of 1 mm. The lithium-containing aluminosilicate glass-ceramic article is not frangible.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 17/024,299, which is a continuation of U.S. application Ser. No. 16/835, 878filed on Mar. 31, 2020, which is a divisional application and claims thebenefit of priority under 35 U.S.C. § 120 of U.S. application Ser. No.16/564, 340 filed on Sep. 9, 2019, which in turn, is a divisionalapplication and claims the benefit of priority under 35 U.S.C. § 120 ofU.S. application Ser. No. 16/181, 815 filed on Nov. 6, 2018, now Pat.No. 10, 427, 975 granted Oct. 1, 2019, which in turn, is a continuationof U.S. application Ser. No. 15/904, 926 filed on Feb. 26, 2018, nowPat. No. 10, 189, 741 granted Jan. 29, 2019, which is a continuation ofU.S. application Ser. No. 14/878, 133 filed on Oct. 8, 2015, now Pat.No. 10, 239, 780 granted Mar. 26, 2019, which claims the benefit ofpriority under 35 U.S.C. § 119 of U.S. Provisional Application SerialNos. 62/205, 120 filed on Aug. 14, 2015 and 62/061, 385 filed on Oct.08, 2014, the contents of each of which are relied upon and incorporatedherein by reference in their entireties.

BACKGROUND Field

Embodiments relate to glass and glass ceramic compositions and inparticular, to high strength glass ceramic compositions having acombination of petalite and lithium silicate phases.

Technical Background

Lithium disilicate glass-ceramics in theSiO₂—Li₂O—K₂O—ZnO—P₂O₅—Al₂O₃—ZrO₂ system have been developed and soldfor use as dental crowns, bridges, and overlays. Their microstructuresof interlocking tabular crystals provide high mechanical strength andfracture toughness and excellent chemical durability. Compositions inthis area were invented at Corning, Inc. and patented by Beall et al. inU.S. Pat. No. 5,219,799 (“the '799 patent”).

In addition, known glass-based materials often exhibit intrinsicbrittleness or low resistance to crack propagation. For example, aninherently low fracture toughness (e.g., 0.5-1.0 MPa·m^(1/2) for oxideglass and glass ceramics) makes oxide glass sensitive to the presence ofsmall defects and flaws. As a comparison point, commercially availablesingle-crystal substrates exhibit a fracture toughness value in therange from about 2.4 to about 4.5 MPa·m^(1/2). Chemical strengtheningby, for example, ion exchange processes can provide some resistance tocrack penetration at the surface of a glass or glass ceramic by imposinga compressive stress layer in the glass or glass ceramic to a depth(e.g., 50-100 μm) from the surface; however, the crack penetrationresistance may be limited and is no longer effective once a crackpropagates through the compressive stress layer into the bulk of theglass or glass ceramic. While the strengthening provides some resistanceto crack penetration, the intrinsic property of the material (k1c) isnot affected by ion exchange. Improvement of the mechanical propertiesof glass-based materials, in particular with respect to damageresistance and fracture toughness, is an ongoing focus. Accordingly,there is a need to provide materials with improved damage resistance andfracture toughness.

Lithium-containing aluminosilicate glass-ceramic articles in theβ-spodumene family that are ion-exchangeable are known that providedamage resistance and fracture toughness. However, β-spodumene basedglass-ceramics are generally opaque, which constrains them fromdisplay-related or other applications requiring transparency ortranslucency. Thus, there is a need for a transparent or translucentglass-ceramic material with fast ion-exchanging capability and highfracture toughness.

BRIEF SUMMARY

A first aspect comprises a glass-ceramic article having a petalitecrystalline phase and a lithium silicate crystalline phase, wherein thepetalite crystalline phase and the lithium silicate crystalline phasehave higher weight percentages than other crystalline phases present inthe glass-ceramic article. In some embodiments, the petalite crystallinephase comprises 20 to 70 wt % of the glass-ceramic article and thelithium silicate crystalline phase comprises 20 to 60 wt % of the glassceramic article. In some embodiments, the petalite crystalline phasecomprises 45 to 70 wt % of the glass-ceramic article and the lithiumsilicate crystalline phase comprises 20 to 50 wt % of the glass ceramicarticle. In some embodiments, the petalite crystalline phase comprises40 to 60 wt % of the glass-ceramic article and the lithium silicatecrystalline phase comprises 20 to 50 wt % of the glass ceramic article.

In some embodiments, the glass-ceramic article is transparent. In someembodiments, the glass-ceramic article has a transmittance of at least85% for light in a wavelength range from 400 nm to 1, 000 nm. In someembodiments, the glass-ceramic article has a transmittance of at least90% for light in a wavelength range from 400 nm to 1, 000 nm. In someembodiments, the glass-ceramic article is transparent. In someembodiments, the glass-ceramic article comprises grains having a longestdimension of 500 nm or less or alternatively 100 nm or less.

In some embodiments, the glass-ceramic has a composition comprising, inwt %:

-   -   SiO₂: 55-80%;    -   Al₂O₃: 2-20%;    -   Li₂O: 5-20%;    -   B₂O₃: 0-10%;    -   Na₂O: 0-5%;    -   ZnO: 0-10%;    -   P₂O₅: 0.5-6%; and    -   ZrO₂: 0.2-15%.

In some embodiments, the glass-ceramic article has a composition furthercomprising, in wt % the following optional additional components:

-   -   K₂O: 0-4%;    -   Mg₀: 0-8%;    -   TiO₂: 0-5%;    -   CeO₂: 0-0.4% and    -   SnO₂: 0.05-0.5%.

In some embodiments, the glass-ceramic article has a compositioncomprising, in wt %:

-   -   SiO₂: 69-80%;    -   Al₂O₃: 6-9%;    -   Li₂O: 10-14%;    -   B₂O₃: 0-2%;    -   P₂O₅: 1.5-2.5%; and    -   ZrO₂: 2-4%.

In some embodiments, the glass-ceramic article has a compositioncomprising, in wt %:

-   -   SiO₂: 69-80%;    -   Al₂O₃: 6-9%;    -   Li₂O: 10-14%;    -   Na₂O: 1-2%;    -   K₂O: 1-2%;    -   B₂O₃: 0-12%;    -   P₂O₅: 1.5-2.5%; and    -   ZrO₂: 2-4%.

In some embodiments, the glass-ceramic article has a compositioncomprising, in wt %:

-   -   SiO₂: 65-80%;    -   Al₂O₃: 5-16%;    -   Li₂O: 8-15%;    -   Na₂O: 0-3%;    -   K₂O: 0-3%;    -   B₂O₃: 0-6%;    -   ZnO: 0-2%;    -   P₂O₅: 0.5-4%; and    -   ZrO₂: 0.2-6%.

In some embodiments, the glass-ceramic article has a compositioncomprising, in wt %:

-   -   SiO₂: 60-80%;    -   Al₂O₃: 5-20%;    -   Li₂O: 5-20%;    -   Na₂O: 0-3%;    -   K₂O: 0-3%;    -   B₂O₃: 0-6%;    -   ZnO: 0-4%;    -   P₂O₅: 0.5-4%; and    -   ZrO₂: 0.2-8%.

In some embodiments, a sum of the weight percentage of P₂O₅ and ZrO₂ inthe glass-ceramic composition is greater than 3.

In some embodiments, the glass-ceramic article has one or more of thefollowing: a fracture toughness of 1 MPa·m^(1/2) or greater, a Vickershardness of about 600 kgf /mm² or greater, or a ring-on-ring strength ofat least 300 MPa. In some embodiments, the glass-ceramic article has acompressive stress layer formed by ion-exchange having a depth of layer(DOL) of at least about 30 μm. In some embodiments, the ion-exchangedglass-ceramic article is not frangible.

A second aspect comprises a method of forming a glass-ceramic article,the method comprises forming a glass composition comprising, in wt %:

-   -   SiO₂: 55-80%;    -   Al₂O₃: 2-20%;    -   Li₂O: 5-20%;    -   B₂O₃: 0-10%;    -   Na₂O: 0-5%;    -   ZnO: 0-10%;    -   P₂O₅: 0.5-6%; and    -   ZrO₂: 0.2 2-15%; and        ceramming the glass composition to form a glass-ceramic article        comprising a petalite crystalline phase and a lithium silicate        crystalline phase, wherein the petalite crystalline phase and        the lithium silicate crystalline phase have higher weight        percentages than other crystalline phases present in the        glass-ceramic article.

In some embodiments the method comprises forming a glass compositionfurther comprising, in wt %:

-   -   K₂O: 0-4%;    -   MgO: 0-8%;    -   TiO₂: 0-5%;    -   CeO₂: 0-0.4% and    -   SnO₂: 0.05-0.5%.

In some embodiments, the method comprises forming a glass compositionthat comprises, in wt %:

-   -   SiO₂: 69-80%;    -   Al₂O₃: 6-9%;    -   Li₂O: 10-14%;    -   B₂O₃: 0-2%;    -   P₂O₅: 1.5-2.5%; and    -   ZrO₂: 2-4%.

In some embodiments, the method comprises forming a glass compositionthat comprises, in wt %:

-   -   SiO₂: 69-80%;    -   Al₂O₃: 6-9%;    -   Li₂O: 10-14%;    -   Na₂O: 1-2%;    -   K₂O: 1-2%;    -   B₂O₃: 0-12%;    -   P₂O₅: 1.5-2.5%; and    -   ZrO₂: 2-4%.

In some embodiments, the method comprises forming a glass compositionthat comprises, in wt %:

-   -   Si02: 65-80%;    -   Al₂O₃: 5-16%;    -   Li₂O: 8-15%;    -   Na₂O: 0-3%;    -   K₂O: 0-3%;    -   B₂O₃: 0-6%;

ZnO: 0-2%;

-   -   P₂O₅: 0.5-4%; and    -   ZrO_(2: 0.2)-6%.

In some embodiments, the method comprises forming a glass compositionthat comprises, in wt %:

SiO2: 60-80%;

-   -   Al₂O₃: 5-20%;    -   Li₂O: 5-20%;    -   Na₂O: 0-3%;    -   K₂O: 0-3%;    -   B₂O₃: 0-6%;    -   ZnO: 0-4%;    -   P₂O₅: 0.5-4%; and    -   ZrO₂: 0.2-8%.

In some embodiments, a sum of the weight percentage of P₂O₅ and ZrO₂ inthe glass composition is greater than 3.

In some embodiments, the method further comprises ion-exchanging theglass-ceramic article to create a compressive stress layer having adepth of layer of at least 30 μm. In some embodiments, the ion-exchangedglass-ceramic article is not frangible.

In some embodiments, ceramming comprises the sequential steps of:heating the glass composition to a glass pre-nucleation temperature;maintaining the glass pre-nucleation temperature for a predeterminedperiod of time; heating the composition to a nucleation temperature;maintaining the nucleation temperature for a predetermined period oftime; heating the composition to a crystallization temperature; andmaintaining the crystallization temperature for a predetermined periodof time.

In some embodiments, ceramming comprises the sequential steps of:heating the composition to a nucleation temperature; maintaining thenucleation temperature for a predetermined period of time; heating thecomposition to a crystallization temperature; and maintaining thecrystallization temperature for a predetermined period of time.

In some embodiments, the method forms a glass-ceramic article whereinthe petalite crystalline phase comprises 20 to 70 wt % of theglass-ceramic article and the lithium silicate crystalline phasecomprises 20 to 60 wt % of the glass ceramic article.

These and other aspects, advantages, and salient features will becomeapparent from the following detailed description, the accompanyingdrawings, and the appended claims.

FIGURES

FIG. 1 is a plot of a differential calorimetry (DSC) trace for anexemplary glass-ceramic composition.

FIG. 2 is a plot of the transmittance of an exemplary glass-ceramiccomposition for light having a wavelength from 400 nm to 1, 000 nm at asample thickness of 1 mm.

FIG. 3A is a scanning electron microscope (SEM) image of an exemplaryglass-ceramic composition on a 200 nm scale.

FIG. 3B is a scanning electron microscope (SEM) image of an exemplaryglass-ceramic composition on a 100 nm scale.

FIG. 4 shows the results of a ring-on-ring (RoR) test and an abradedring-on-ring (aRoR) test of an exemplary non-ion-exchanged glass-ceramiccomposition.

FIG. 5 shows a plot of concentration of Na₂O in mole percent vs.thickness of the sample for an exemplary glass-ceramic composition.

FIG. 6 shows the results of a RoR test of an exemplary glass-ceramiccomposition before and after ion-exchanging.

FIG. 7 shows the results of an aRoR test of an exemplary glass-ceramiccomposition that has been ion-exchanged.

FIG. 8 shows the results of a RoR test of an exemplary glass-ceramiccomposition ion-exchanged for different durations of time.

FIG. 9 shows the results of an aRoR test of an exemplary glass-ceramiccomposition that has been ion-exchanged and abraded under differentpressures.

FIG. 10 is a photograph showing ion-exchanged glass-ceramic sheets withdifferent break patterns.

FIG. 11 is a plot of a differential calorimetry (DSC) trace for anexemplary glass-ceramic composition.

FIG. 12 shows an X-ray diffraction (XRD) spectra of the crystallinephases of an exemplary glass-ceramic composition.

FIG. 13 shows the results of a ring-on-ring (RoR) test of an exemplaryglass-ceramic composition.

FIG. 14 shows a plot of concentration of Na₂O in weight percent vs.thickness of the sample for an exemplary glass-ceramic composition.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details may beset forth in order to provide a thorough understanding of embodimentsdescribed herein. However, it will be clear to one skilled in the artwhen embodiments may be practiced without some or all of these specificdetails. In other instances, well-known features or processes may not bedescribed in detail so as not to unnecessarily obscure the disclosure.In addition, like or identical reference numerals may be used toidentify common or similar elements. Moreover, unless otherwise defined,all technical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skill in the art to which thisdisclosure belongs. In case of conflict, the present specification,including the definitions herein, will control.

Although other methods and materials can be used in the practice ortesting of the embodiments, certain suitable methods and materials aredescribed herein.

Disclosed are materials, compounds, compositions, and components thatcan be used for, can be used in conjunction with, can be used inpreparation for, or are embodiments of the disclosed method andcompositions. These and other materials are disclosed herein, and it isunderstood that when combinations, subsets, interactions, groups, etc.of these materials are disclosed that while specific reference of eachvarious individual and collective combinations and permutation of thesecompounds may not be explicitly disclosed, each is specificallycontemplated and described herein.

Thus, if a class of substituents A, B, and C are disclosed as well as aclass of substituents D, E, and F, and an example of a combinationembodiment, A-D is disclosed, then each is individually and collectivelycontemplated. Thus, in this example, each of the combinations A-E, A-F,B-D, B-E, B-F, C-D, C-E, and C-F are specifically contemplated andshould be considered disclosed from disclosure of A, B, and/or C; D, E,and/or F; and the example combination A-D. Likewise, any subset orcombination of these is also specifically contemplated and disclosed.Thus, for example, the sub-group of A-E, B-F, and C-E are specificallycontemplated and should be considered disclosed from disclosure of A, B,and/or C; D, E, and/or F; and the example combination A-D. This conceptapplies to all aspects of this disclosure including, but not limited toany components of the compositions and steps in methods of making andusing the disclosed compositions. More specifically, the examplecomposition ranges given herein are considered part of the specificationand further, are considered to provide example numerical rangeendpoints, equivalent in all respects to their specific inclusion in thetext, and all combinations are specifically contemplated and disclosed.Further, if there are a variety of additional steps that can beperformed it is understood that each of these additional steps can beperformed with any specific embodiment or combination of embodiments ofthe disclosed methods, and that each such combination is specificallycontemplated and should be considered disclosed.

Moreover, where a range of numerical values is recited herein,comprising upper and lower values, unless otherwise stated in specificcircumstances, the range is intended to include the endpoints thereof,and all integers and fractions within the range. It is not intended thatthe scope of the disclosure be limited to the specific values recitedwhen defining a range. Further, when an amount, concentration, or othervalue or parameter is given as a range, one or more preferred ranges ora list of upper preferable values and lower preferable values, this isto be understood as specifically disclosing all ranges formed from anypair of any upper range limit or preferred value and any lower rangelimit or preferred value, regardless of whether such pairs areseparately disclosed. Finally, when the term “about” is used indescribing a value or an end-point of a range, the disclosure should beunderstood to include the specific value or end-point referred to.

As used herein, the term “about” means that amounts, sizes,formulations, parameters, and other quantities and characteristics arenot and need not be exact, but may be approximate and/or larger orsmaller, as desired, reflecting tolerances, conversion factors, roundingoff, measurement error and the like, and other factors known to those ofskill in the art. In general, an amount, size, formulation, parameter orother quantity or characteristic is “about” or “approximate” whether ornot expressly stated to be such.

The term “or”, as used herein, is inclusive; more specifically, thephrase “A or B” means “A, B, or both A and B.” Exclusive “or” isdesignated herein by terms such as “either A or B” and “one of A or B, ”for example.

The indefinite articles “a” and “an” are employed to describe elementsand components of the disclosure. The use of these articles means thatone or at least one of these elements or components is present. Althoughthese articles are conventionally employed to signify that the modifiednoun is a singular noun, as used herein the articles “a” and “an” alsoinclude the plural, unless otherwise stated in specific instances.Similarly, the definite article “the”, as used herein, also signifiesthat the modified noun may be singular or plural, again unless otherwisestated in specific instances.

For the purposes of describing the embodiments, it is noted thatreference herein to a variable being a “function” of a parameter oranother variable is not intended to denote that the variable isexclusively a function of the listed parameter or variable. Rather,reference herein to a variable that is a “function” of a listedparameter is intended to be open ended such that the variable may be afunction of a single parameter or a plurality of parameters.

It is noted that terms like “preferably, ” “commonly, ” and “typically,” when utilized herein, are not utilized to limit the scope of thedisclosure or to imply that certain features are critical, essential, oreven important to the structure or function of the disclosure. Rather,these terms are merely intended to identify particular aspects of anembodiment of the present disclosure or to emphasize alternative oradditional features that may or may not be utilized in a particularembodiment of the present disclosure.

It is noted that one or more of the claims may utilize the term“wherein” as a transitional phrase. For the purposes of defining thepresent disclosure, it is noted that this term is introduced in theclaims as an open-ended transitional phrase that is used to introduce arecitation of a series of characteristics of the structure and should beinterpreted in like manner as the more commonly used open-ended preambleterm “comprising.”

As a result of the raw materials and/or equipment used to produce theglass or glass ceramic composition of the present disclosure, certainimpurities or components that are not intentionally added, can bepresent in the final glass or glass ceramic composition. Such materialsare present in the glass or glass ceramic composition in minor amountsand are referred to herein as “tramp materials.”

As used herein, a glass or glass ceramic composition having 0 wt % of acompound is defined as meaning that the compound, molecule, or elementwas not purposefully added to the composition, but the composition maystill comprise the compound, typically in tramp or trace amounts.Similarly, “iron-free, ” “sodium-free, ” “lithium-free, ”“zirconium-free, ” “alkali earth metal-free, ” “heavy metal-free” or thelike are defined to mean that the compound, molecule, or element was notpurposefully added to the composition, but the composition may stillcomprise iron, sodium, lithium, zirconium, alkali earth metals, or heavymetals, etc., but in approximately tramp or trace amounts.

Unless otherwise specified, the concentrations of all constituentsrecited herein are expressed in terms of weight percent (wt %).

Glasses and Glass Ceramics

As noted previously, it is desirable to obtain a transparent ortranslucent lithium-containing aluminosilicate glass ceramic compositionthat has petalite and lithium silicate as the primary crystal phases.The lithium silicate crystal phase may be lithium disilicate or lithiummetasilicate. Improved properties of the glass and glass ceramiccompositions disclosed herein include: 1) the glass retains a lowmelting temperature (below 1500° C.), yet provides a higher liquidusviscosity (>2000 poise) and a long working range that is compatible withconventional rolling, molding, and float processes; 2) lithium silicateis retained as a major crystal phase, providing inherently highmechanical strength and fracture toughness to the glass-ceramic; and 3)petalite is a second major crystal phase and has a fine grain size,which contributes to the transparency or translucency of theglass-ceramic, and also can be ion-exchanged for additional mechanicalstrength. Additionally, the materials can be cerammed into shapes withminimal deformation, readily machined to precision shapes, cut, drilled,chamfered, tapped, polished to high luster with conventional ceramicmachining tooling and even exhibit various degrees of translucencydepending on composition and heat treatment. These properties make theglass ceramics useful for a broad number of applications, such ascountertops and other surfaces, hand-held, desk-top, and wall-mountedconsumer electronic device coverings, appliance doors and exteriors,floor tiles, wall panels, ceiling tiles, white boards, materials storagecontainers (holloware) such as beverage bottles, food sales and storagevessels, machine parts requiring light weight, good wear resistance andprecise dimensions. The glass ceramics can be formed inthree-dimensional articles using various methods due to its lowerviscosity.

Petalite, LiAlSi₄O₁₀, is a monoclinic crystal possessing athree-dimensional framework structure with a layered structure havingfolded Si₂O₅ layers linked by Li and Al tetrahedra. The Li is intetrahedral coordination with oxygen. The mineral petalite is a lithiumsource and is used as a low thermal expansion phase to improve thethermal downshock resistance of glass-ceramic or ceramic parts.Moreover, glass-ceramic articles based on the petalite phase can bechemically strengthened in a salt bath, during which Na+ (and/or K+)replaces Li+ in the petalite structure, which causes surface compressionand strengthening. In some embodiments, the weight percentage of thepetalite crystalline phase in the glass-ceramic compositions can be in arange from about 20 to about 70 wt %, about 20 to about 65 wt %, about20 to about 60 wt %, about 20 to about 55 wt %, about 20 to about 50 wt%, about 20 to about 45 wt %, about 20 to about 40 wt %, about 20 toabout 35 wt %, about 20 to about 30 wt %, about 20 to about 25 wt %,about 25 to about 70 wt %, about 25 to about 65 wt %, about 25 to about60 wt %, about 25 to about 55 wt %, about 25 to about 50 wt %, about 25to about 45 wt %, about 25 to about 40 wt %, about 25 to about 35 wt %,about 25 to about 30 wt %, about 30 to about 70 wt %, about 30 to about65 wt %, about 30 to about 60 wt %, about 30 to about 55 wt %, about 30to about 50 wt %, about 30 to about 45 wt %, about 30 to about 40 wt %,about 30 to about 35 wt %, about 35 to about 70 wt %, about 35 to about65 wt %, about 35 to about 60 wt %, about 35 to about 55 wt %, about 35to about 50 wt %, about 35 to about 45 wt %, about 35 to about 40 wt %,about 40 to about 70 wt %, about 40 to about 65 wt %, about 40 to about60 wt %, about 40 to about 55 wt %, about 40 to about 50 wt %, about 40to about 45 wt %, about 45 to about 70 wt %, about 45 to about 65 wt %,about 45 to about 60 wt %, about 45 to about 55 wt %, about 45 to about50 wt %, about 50 to about 70 wt %, about 50 to about 65 wt %, about 50to about 60 wt %, about 50 to about 55 wt %, about 55 to about 70 wt %,about 55 to about 65 wt %, about 55 to about 60 wt %, about 60 to about70 wt %, about 60 to about 65 wt %, or about 65 to about 70 wt %. Insome embodiments, the glass-ceramic has about 20, 21, 22, 23, 24, 25 ,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,62, 63, 64, 65, 66, 67, 68, 69, or 70 wt % petatlite crystalline phase.

As noted above, the lithium silicate crystalline phase may be lithiumdisilicate or lithium metasilicate. Lithium disilicate, Li₂Si₂O₅, is anorthorhombic crystal based on corrugated sheets of {Si₂O₅} tetrahedralarrays. The crystals are typically tabular or lath-like in shape, withpronounced cleavage planes. Glass-ceramics based on lithium disilicateoffer highly desirable mechanical properties, including high bodystrength and fracture toughness, due to their microstructures ofrandomly-oriented interlocked crystals—a crystal structure that forcescracks to propagate through the material via tortuous paths around thesecrystals. Lithium metasilicate, Li₂SiO₃, has an orthorhombic symmetrywith (Si₂O₆) chains running parallel to the c axis and linked togetherby lithium ions. Lithium metasilicate crystals can be easily dissolvedfrom glass-ceramics in diluted hydrofluoric acid. In some embodiments,the weight percentage of the lithium silicate crystalline phase in theglass-ceramic compositions can be in a range from about 20 to about 60wt %, about 20 to about 55 wt %, about 20 to about 50 wt %, about 20 toabout 45 wt %, about 20 to about 40 wt %, about 20 to about 35 wt %,about 20 to about 30 wt %, about 20 to about 25 wt %, about 25 to about60 wt %, about 25 to about 55 wt %, about 25 to about 50 wt %, about 25to about 45 wt %, about 25 to about 40 wt %, about 25 to about 35 wt %,about 25 to about 30 wt %, about 30 to about 60 wt %, about 30 to about55 wt %, about 30 to about 50 wt %, about 30 to about 45 wt %, about 30to about 40 wt %, about 30 to about 35 wt %, about 35 to about 60 wt %,about 35 to about 55 wt %, about 35 to about 50 wt %, about 35 to about45 wt %, about 35 to about 40 wt %, about 40 to about 60 wt %, about 40to about 55 wt %, about 40 to about 50 wt %, about 40 to about 45 wt %,about 45 to about 60 wt %, about 45 to about 55 wt %, about 45 to about50 wt %, about 50 to about 60 wt %, about 50 to about 55 wt %, or about55 to about 60 wt %. In some embodiments, the glass-ceramic has 20, 21,22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38 , 39,40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57,58, 59, or 60 wt % lithium silicate crystalline phase.

There are two broad families of lithium disilicate glass-ceramics. Thefirst group comprises those that are doped with ceria and a noble metalsuch as silver. These can be photosensitively nucleated via UV light andsubsequently heat-treated to produce strong glass-ceramics such asFotoceram®. The second family of lithium disilicate glass-ceramics isnucleated by the addition of P₂O₅, wherein the nucleating phase isLi₃PO₄. P₂O₅-nucleated lithium disilicate glass-ceramics have beendeveloped for applications as varied as high-temperature sealingmaterials, disks for computer hard drives, transparent armor, and dentalapplications.

The glasses and glass ceramics described herein may be genericallydescribed as lithium-containing aluminosilicate glasses or glassceramics and comprise SiO₂, Al₂O₃, and Li₂O. In addition to SiO₂, Al₂O₃,and Li₂O, the glasses and glass ceramics embodied herein may furthercontain alkali salts, such as Na₂O, K₂O, Rb₂O, or Cs₂O, as well as P₂O₅,and ZrO₂ and a number of other components as described below. In one ormore embodiments, the major crystallite phases include petalite andlithium silicate, but β-spodumene ss, β-quartz ss, lithium phosphate,cristobalite, and rutile may also be present as minor phases dependingon the compositions of the precursor glass. In some embodiments, theglass-ceramic composition has a residual glass content of about 5 toabout 30 wt %, about 5 to about 25 wt %, about 5 to about 20 wt %, about5 to about 15 wt % about 5 to about 10 wt %, about 10 to about 30 wt %,about 10 to about 25 wt %, about 10 to about 20 wt %, about 10 to about15 wt %, about 15 to about 30 wt %, about 15 to about 25 wt %, about 15to about 20 wt %, about 20 to about 30 wt % about 20 to about 25 wt %,or about 25 to about 30 wt %. In some embodiments the residual glasscontent can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 wt %.

SiO₂, an oxide involved in the formation of glass, can function tostabilize the networking structure of glasses and glass ceramics. Insome embodiments, the glass or glass ceramic composition comprises fromabout 55 to about 80 wt % SiO₂. In some embodiments, the glass or glassceramic composition comprises from 69 to about 80 wt % SiO₂. In someembodiments, the glass or glass ceramic composition can comprise fromabout 55 to about 80 wt %, about 55 to about 77 wt %, about 55 to about75 wt %, about 55 to about 73 wt %, 60 to about 80 wt %, about 60 toabout 77 wt %, about 60 to about 75 wt %, about 60 to about 73 wt %, 65to about 80 wt %, about 65 to about 77 wt %, about 65 to about 75 wt %,about 65 to about 73 wt %, 69 to about 80 wt %, about 69 to about 77 wt%, about 69 to about 75 wt %, about 69 to about 73 wt %, about 70 toabout 80 wt %, about 70 to about 77 wt %, about 70 to about 75 wt %,about 70 to about 73 wt %, about 73 to about 80 wt %, about 73 to about77 wt %, about 73 to about 75 wt %, about 75 to about 80 wt %, about 75to about 77 wt %, or about 77 to about 80 wt %, SiO₂. In someembodiments, the glass or glass ceramic composition comprises about 55,56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73,74, 75, 76, 77, 78, 79, or 80, wt % SiO₂.

With respect to viscosity and mechanical performance, the viscosity andmechanical performance are influenced by glass compositions. In theglasses and glass ceramics, SiO₂ serves as the primary glass-formingoxide for the precursor glass and can function to stabilize thenetworking structure of glass and glass ceramic. The concentration ofSiO₂ should be sufficiently high in order to form petalite crystal phasewhen the precursor glass is heat treated to convert to a glass-ceramic.The amount of SiO₂ may be limited to control melting temperature (200poise temperature), as the melting temperature of pure SiO₂ or high-SiO₂glasses is undesirably high.

Al₂O₃ may also provide stabilization to the network and also providesimproved mechanical properties and chemical durability. If the amount ofAl₂O₃ is too high, however, the fraction of lithium silicate crystalsmay be decreased, possibly to the extent that an interlocking structurecannot be formed. The amount of Al₂O₃ can be tailored to controlviscosity. Further, if the amount of Al₂O₃ is too high, the viscosity ofthe melt is also generally increased. In some embodiments, the glass orglass ceramic composition can comprise from about 2 to about 20 wt %Al₂O₃. In some embodiments, the glass or glass ceramic composition cancomprise from about 6 to about 9 wt % Al₂O₃. In some embodiments, theglass or glass ceramic composition can comprise from about 2 to about20%, about 2 to about 18 wt %, about 2 to about 15 wt %, about 2 toabout 12 wt %, about 2 to about 10 wt %, about 2 to about 9 wt %, about2 to about 8 wt %, about 2 to about 5 wt %, about 5 to about 20%, about5 to about 18 wt %, about 5 to about 15 wt %, about 5 to about 12 wt %,about 5 to about 10 wt %, about 5 to about 9 wt %, about 5 to about 8 wt%, about 6 to about 20%, about 6 to about 18 wt %, about 6 to about 15wt %, about 6 to about 12 wt %, about 6 to about 10 wt %, about 6 toabout 9 wt %, about 8 to about 20%, about 8 to about 18 wt %, about 8 toabout 15 wt %, about 8 to about 12 wt %, about 8 to about 10 wt %, about10 to about 20%, about 10 to about 18 wt %, about 10 to about 15 wt %,about 10 to about 12 wt %, about 12 to about 20%, about 12 to about 18wt %, or about 12 to about 15 wt %, Al₂O₃. In some embodiments, theglass or glass ceramic composition can comprise about 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 wt % Al₂O₃.

In the glass and glass ceramics herein, Li₂O aids in forming bothpetalite and lithium silicate crystal phases. In fact, to obtainpetalite and lithium silicate as the predominant crystal phases, it isdesirable to have at least about 7 wt % Li₂O in the composition.Additionally, it has been found that once Li₂O gets too high—greaterthan about 15 wt %—the composition becomes very fluid. In some embodiedcompositions, the glass or glass ceramic can comprise from about 5 wt %to about 20 wt % Li₂O. In other embodiments, the glass or glass ceramiccan comprise from about 10 wt % to about 14 wt % Li₂O. In someembodiments, the glass or glass ceramic composition can comprise fromabout 5 to about 20 wt %, about 5 to about 18 wt %, about 5 to about 16wt %, about 5 to about 14 wt %, about 5 to about 12 wt %, about 5 toabout 10 wt %, about 5 to about 8 wt %, 7 to about 20 wt %, about 7 toabout 18 wt %, about 7 to about 16 wt %, about 7 to about 14 wt %, about7 to about 12 wt %, about 7 to about 10 wt %, 10 to about 20 wt %, about10 to about 18 wt %, about 10 to about 16 wt %, about 10 to about 14 wt%, about 10 to about 12 wt %, 12 to about 20 wt %, about 12 to about 18wt %, about 12 to about 16 wt %, about 12 to about 14 wt %, 14 to about20 wt %, about 14 to about 18 wt %, about 14 to about 16 wt %, about 16to about 20 wt %, about 16 to about 18 wt %, or about 18 to about 20 wt% Li₂O. In some embodiments, the glass or glass ceramic composition cancomprise about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or20 wt % Li₂O.

As noted above, Li₂O is generally useful for forming the embodied glassceramics, but the other alkali oxides tend to decrease glass ceramicformation and form an aluminosilicate residual glass in theglass-ceramic. It has been found that more than about 5 wt % Na₂O orK₂O, or combinations thereof, leads to an undesirable amount of residualglass which can lead to deformation during crystallization andundesirable microstructures from a mechanical property perspective. Thecomposition of the residual glass may be tailored to control viscosityduring crystallization, minimizing deformation or undesirable thermalexpansion, or control microstructure properties. Therefore, in general,the compositions described herein have low amounts of non-lithium alkalioxides. In some embodiments, the glass or glass ceramic composition cancomprise from about 0 to about 5 wt % R₂O, wherein R is one or more ofthe alkali cations Na and K. In some embodiments, the glass or glassceramic composition can comprise from about 1 to about 3 wt % R₂O,wherein R is one or more of the alkali cations Na and K. In someembodiments, the glass or glass ceramic composition can comprise from 0to about 5 wt %, 0 to 4 wt %, 0 to 3 wt %, 0 to about 2 wt %, 0 to about1 wt %, >0 to about 5 wt %, >0 to about 4 wt %, >0 to about 3 wt %, >0to about 2 wt %, >0 to about 1 wt %, about 1 to about 5 wt %, about 1 toabout 4 wt %, about 1 to about 3 wt %, about 1 to about 2 wt %, about 2to about 5 wt %, about 2 to about 4 wt %, about 2 to about 3 wt %, about3 to about 5 wt %, about 3 to about 4 wt %, or about 4 to about 5 wt %Na₂O or K₂O, or combinations thereof. In some embodiments, the glass orglass ceramic composition can comprise about 0, >0, 1, 2, 3, 4, or 5 wt% R₂O.

The glass and glass ceramic compositions can include P₂O₅. P₂O₅ canfunction as a nucleating agent to produce bulk nucleation. If theconcentration of P₂O₅ is too low, the precursor glass does crystallize,but only at higher temperatures (due to a lower viscosity) and from thesurface inward, yielding a weak and often deformed body; however, if theconcentration of P₂O₅ is too high, the devitrification, upon coolingduring precursor glass forming, can be difficult to control. Embodimentscan comprise from >0 to about 6 wt % P₂O₅. Other embodiments cancomprise about 2 to about 4 wt % P₂O₅. Still other embodiments cancomprise about 1.5 to about 2.5 wt % P₂O₅. Embodied compositions cancomprise from 0 to about 6 wt %, 0 to about 5.5 wt %, 0 to about 5 wt %,0 to about 4.5 wt %, 0 to about 4 wt %, 0 to about 3.5 wt %, 0 to about3 wt %, 0 to about 2.5 wt %, 0 to about 2 wt %, 0 to about 1.5 wt %, 0to about 1 wt %, >0 to about 6 wt %, >0 to about 5.5 wt %, >0 to about 5wt %, >0 to about 4.5 wt %, >0 to about 4 wt %, >0 to about 3.5 wt %, >0to about 3 wt %, >0 to about 2.5 wt %, >0 to about 2 wt %, >0 to about1.5 wt %, >0 to about 1 wt %, about 0.5 to about 6 wt %, about 0.5 toabout 5.5 wt %, about 0.5 to about 5 wt %, about 0.5 to about 4.5 wt %,about 0.5 to about 4 wt %, about 0.5 to about 3.5 wt, about 0.5 to about3 wt %, about 0.5 to about 2.5 wt %, about 0.5 to about 2 wt %, about0.5 to about 1.5 wt %, about 0.5 to about 1 wt %, about 1 to about 6 wt%, about 1 to about 5.5 wt %, about 1 to about 5 wt %, about 1 to about4.5 wt %, about 1 to about 4 wt %, about 1 to about 3.5 wt %, about 1 toabout 3 wt %, about 1 to about 2.5 wt %, about 1 to about 2 wt %, about1 to about 1.5 wt %, about 1.5 to about 6 wt %, about 1.5 to about 5.5wt %, about 1.5 to about 5 wt %, about 1.5 to about 4.5 wt %, about 1.5to about 4 wt %, about 1.5 to about 3.5 wt %, about 1.5 to about 3 wt %,about 1.5 to about 2.5 wt %, about 1.5 to about 2 wt %, about 2 to about6 wt %, about 2 to about 5.5 wt %, about 2 to about 5 wt %, about 2 toabout 4.5 wt %, about 2 to about 4 wt %, about 2 to about 3.5 wt %,about 2 to about 3 wt %, about 2 to about 2.5 wt %, about 2.5 to about 6wt %, about 2.5 to about 5.5 wt %, about 2.5 to about 5 wt %, about 2.5to about 4.5 wt %, about 2.5 to about 4 wt %, about 2.5 to about 3.5 wt%, about 2.5 to about 3 wt %, about 3 to about 6 wt %, about 3 to about5.5 wt %, about 3 to about 5 wt %, about 3 to about 4.5 wt %, about 3 toabout 4 wt %, about 3 to about 3.5 wt %, about 3.5 to about 6 wt %,about 3.5 to about 5.5 wt %, about 3.5 to about 5 wt %, about 3.5 toabout 4.5 wt %, about 3.5 to about 4 wt %, about 4 to about 6 wt %,about 4 to about 5.5 wt %, about 4 to about 5 wt %, about 4 to about 4.5wt %, about 4.5 to about 6 wt %, about 4.5 to about 5.5 wt %, about 4.5to about 5 wt %, about 5 to about 6 wt %, about 5 to about 5.5 wt %, orabout 5.5 to about 6 wt % P₂O₅. In some embodiments, the glass or glassceramic composition can comprise about 0, >0, 0.5, 1, 1.5, 2, 2.5, 3,3.5, 4, 4.5, 5, 5.5, or 6 wt % P₂O₅.

In the glass and glass ceramics herein, it is generally found that ZrO₂can improve the stability of Li₂O—Al₂O₃—SiO₂—P₂O₅ glass by significantlyreducing glass devitrification during forming and lowering liquidustemperature. At concentrations above 8 wt %, ZrSiO₄ can form a primaryliquidus phase at a high temperature, which significantly lowersliquidus viscosity. Transparent glasses can be formed when the glasscontains over 2 wt % ZrO₂. The addition of ZrO₂ can also help decreasethe petalite grain size, which aids in the formation of a transparentglass-ceramic. In some embodiments, the glass or glass ceramiccomposition can comprise from about 0.2 to about 15 wt % ZrO₂. In someembodiments, the glass or glass ceramic composition can be from about 2to about 4 wt % ZrO₂. In some embodiments, the glass or glass ceramiccomposition can comprise from about 0.2 to about 15 wt %, about 0.2 toabout 12 wt %, about 0.2 to about 10 wt %, about 0.2 to about 8 wt %,about 0.2 to 6 wt %, about 0.2 to about 4 wt %, 0.5 to about 15 wt %,about 0.5 to about 12 wt %, about 0.5 to about 10 wt %, about 0.5 toabout 8 wt %, about 0.5 to 6 wt %, about 0.5 to about 4 wt %, 1 to about15 wt %, about 1 to about 12 wt %, about 1 to about 10 wt %, about 1 toabout 8 wt %, about 1 to 6 wt %, about 1 to about 4 wt %, 2 to about 15wt %, about 2 to about 12 wt %, about 2 to about 10 wt %, about 2 toabout 8 wt %, about 2 to 6 wt %, about 2 to about 4 wt %, about 3 toabout 15 wt %, about 3 to about 12 wt %, about 3 to about 10 wt %, about3 to about 8 wt %, about 3 to 6 wt %, about 3 to about 4 wt %, about 4to about 15 wt %, about 4 to about 12 wt %, about 4 to about 10 wt %,about 4 to about 8 wt %, about 4 to 6 wt %, about 8 to about 15 wt %,about 8 to about 12 wt %, about 8 to about 10 wt %, about 10 to about 15wt %, about 10 to about 12 wt %, or about 12 to about 15 wt % ZrO₂. Insome embodiments, the glass or glass ceramic composition can compriseabout 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 wt% ZrO₂.

B₂O₃ is conducive to providing a precursor glass with a low meltingtemperature. Furthermore, the addition of B₂O₃ in the precursor glassand thus the glass-ceramics helps achieve an interlocking crystalmicrostructure and can also improve the damage resistance of the glassceramic. When boron in the residual glass is not charge balanced byalkali oxides or divalent cation oxides, it will be intrigonal-coordination state (or three-coordinated boron), which opens upthe structure of the glass. The network around these three-coordinatedboron is not as rigid as tetrahedrally coordinated (or four-coordinated)boron. Without being bound by theory, it is believed that precursorglasses and glass ceramics that include three-coordinated boron cantolerate some degree of deformation before crack formation. Bytolerating some deformation, the Vickers indentation crack initiationvalues are increased. Fracture toughness of the precursor glasses andglass ceramics that include three-coordinated boron may also beincreased. Without being bound by theory, it is believed that thepresence of boron in the residual glass of the glass ceramic (andprecursor glass) lowers the viscosity of the residual glass (orprecursor glass), which facilitates the growth of lithium silicatecrystals, especially large crystals having a high aspect ratio. Agreater amount of three-coordinated boron (in relation tofour-coordinated boron) is believed to result in glass ceramics thatexhibit a greater Vickers indentation crack initiation load. In someembodiments, the amount of three-coordinated boron (as a percent oftotal B₂O₃) may be about 40% or greater, 50% or greater, 75% or greater,about 85% or greater or even about 95% or greater. The amount of boronin general should be controlled to maintain chemical durability andmechanical strength of the cerammed bulk glass ceramic.

In one or more embodiments, the glasses and glass ceramic herein cancomprise from 0 to about 10 wt % or from 0 to about 2 wt % B₂O₃. In someembodiments, the glass or glass ceramic composition can comprise from 0to about 10 wt %, 0 to about 9 wt %, 0 to about 8 wt %, 0 to about 7 wt%, 0 to about 6 wt %, 0 to about 5 wt %, 0 to about 4 wt %, 0 0 to about3 wt %, 0 to about 2 wt %, 0 to about 1 wt %, >0 to about 10 wt %, >0 toabout 9 wt %, >0 to about 8 wt %, >0 to about 7 wt %, >0 to about 6 wt%, >0 to about 5 wt %, >0 to about 4 wt %, >0 to about 3 wt %, >0 toabout 2 wt %, >0 to about 1 wt %, about 1 to about 10 wt %, about 1 toabout 8 wt %, about 1 to about 6 wt %, about 1 to about 5 wt %, about 1to about 4 wt %, about 1 to about 2 wt %, about 2 to about 10 wt %,about 2 to about 8 wt %, about 2 to about 6 wt %, about 2 to about 4 wt%, about 3 to about 10 wt %, about 3 to about 8 wt %, about 3 to about 6wt %, about 3 to about 4 wt %, about 4 to about 5 wt %, about 5 wt % toabout 8 wt %, about 5 wt % to about 7.5 wt %, about 5 wt % to about 6 wt%, or about 5 wt % to about 5.5 wt % B₂O₃. In some embodiments, theglass or glass ceramic composition can comprise about 0, >0, 1, 2, 3, 4,5, 6, 7, 8, 9, or 10 wt % B₂O₃.

MgO can enter petalite crystals in a partial solid solution. In one ormore embodiments, the glasses and glass ceramic herein can comprise from0 to about 8 wt % MgO. In some embodiments, the glass or glass ceramiccomposition can comprise from 0 to about 8 wt %, 0 to about 7 wt %, 0 toabout 6 wt %, 0 to about 5 wt %, 0 to about 4 wt %, 0 to about 3 wt %, 0to about 2 wt %, 0 to about 1 wt %, about 1 to about 8 wt %, about 1 toabout 7 wt %, about 1 to about 6 wt %, about 1 to about 5 wt %, about 1to about 4 wt %, about 1 to about 3 wt %, about 1 to about 2 wt %, about2 to about 8 wt %, about 2 to about 7 wt %, about 2 to about 6 wt %,about 2 to about 5 wt %, about 2 to about 4 wt %, about 2 to about 3 wt%, about 3 to about 8 wt %, about 3 to about 7 wt %, about 3 to about 6wt %, about 3 to about 5 wt %, about 3 to about 4 wt %, about 4 to about8 wt %, about 4 to about 7 wt %, about 4 to about 6 wt %, about 4 toabout 5 wt %, about 5 to about 8 wt %, about 5 to about 7 wt %, about 5to about 6 wt %, about 6 to about 8 wt %, about 6 to about 7 wt %, orabout 7 wt % to about 8 wt % MgO. In some embodiments, the glass orglass ceramic composition can comprise about 0, >0, 1, 2, 3, 4, 5, 6, 7,or 8 wt % MgO.

ZnO can enter petalite crystals in a partial solid solution. In one ormore embodiments, the glasses and glass ceramics herein can comprisefrom 0 to about 10 wt % ZnO. In some embodiments, the glass or glassceramic composition can comprise from 0 to about 10 wt %, 0 to about 9wt %, 0 to about 8 wt %, 0 to about 7 wt %, 0 to about 6 wt %, 0 toabout 5 wt %, 0 to about 4 wt %, 0 to about 3 wt %, 0 to about 2 wt %, 0to about 1 wt %, about 1 to about 10 wt %, about 1 to about 9 wt %,about 1 to about 8 wt %, about 1 to about 7 wt %, about 1 to about 6 wt%, about 1 to about 5 wt %, about 1 to about 4 wt %, about 1 to about 3wt %, about 1 to about 2 wt %, about 2 to about 10 wt %, about 2 toabout 9 wt %, about 2 to about 8 wt %, about 2 to about 7 wt %, about 2to about 6 wt %, about 2 to about 5 wt %, about 2 to about 4 wt %, about2 to about 3 wt %, about 3 to about 10 wt %, about 3 to about 9 wt %,about 3 to about 8 wt %, about 3 to about 7 wt %, about 3 to about 6 wt%, about 3 to about 5 wt %, about 3 to about 4 wt %, about 4 to about 10wt %, about 4 to about 9 wt %, about 4 to about 8 wt %, about 4 to about7 wt %, about 4 to about 6 wt %, about 4 to about 5 wt %, about 5 toabout 10 wt %, about 5 to about 9 wt %, about 5 to about 8 wt %, about 5to about 7 wt %, about 5 to about 6 wt %, about 6 to about 10 wt %,about 6 to about 9 wt %, about 6 to about 8 wt %, about 6 to about 7 wt%, about 7 to about 10 wt %, about 7 to about 9 wt %, about 7 wt % toabout 8 wt %, about 8 to about 10 wt %, about 8 to about 9 wt %, orabout 9 to about 10 wt % ZnO. In some embodiments, the glass or glassceramic composition can comprise about 0, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9,or 10 wt % ZnO.

In one or more embodiments, the glasses and glass ceramics herein cancomprise from 0 to about 5 wt % TiO₂. In some embodiments, the glass orglass ceramic composition can comprise from 0 to about 5 wt %, 0 toabout 4 wt %, 0 to about 3 wt %, 0 to about 2 wt %, 0 to about 1 wt %,about 1 to about 5 wt %, about 1 to about 4 wt %, about 1 to about 3 wt%, about 1 to about 2 wt %, about 2 to about 5 wt %, about 2 to about 4wt %, about 2 to about 3 wt %, about 3 to about 5 wt %, about 3 to about4 wt %, or about 4 to about 5 wt % TiO₂. In some embodiments, the glassor glass ceramic composition can comprise about 0, >0, 1, 2, 3, 4, or 5wt % TiO₂.

In one or more embodiments, the glasses and glass ceramics herein cancomprise from 0 to about 0.4 wt % CeO₂. In some embodiments, the glassor glass ceramic composition can comprise from 0 to about 0.4 wt %, 0 toabout 0.3 wt %, 0 to about 0.2 wt %, 0 to about 0.1 wt %, about 0.1 toabout 0.4 wt %, about 1 to about 0.3 wt %, about 1 to about 0.2 wt %,about 0.2 to about 0.4 wt %, about 0.2 to about 0.3 wt %, or about 0.3to about 0.4 wt % CeO₂. In some embodiments, the glass or glass ceramiccomposition can comprise about 0, >0, 0.1, 0.2, 0.3, or 0.4 wt % CeO₂.

In one or more embodiments, the glasses and glass ceramics herein cancomprise from 0 to about 0.5 wt % SnO₂. In some embodiments, the glassor glass ceramic composition can comprise from 0 to about 0.5 wt %, 0 toabout 0.4 wt %, 0 to about 0.3 wt %, 0 to about 0.2 wt %, 0 to about 0.1wt %, about 0.05 to about 0.5 wt %, 0.05 to about 0.4 wt %, 0.05 toabout 0.3 wt %, 0.05 to about 0.2 wt %, 0.05 to about 0.1 wt %, about0.1 to about 0.5 wt %, about 0.1 to about 0.4 wt %, about 0.1 to about0.3 wt %, about 0.1 to about 0.2 wt %, about 0.2 to about 0.5 wt %,about 0.2 to about 0.4 wt %, about 0.2 to about 0.3 wt %, about 0.3 toabout 0.5 wt %, about 0.3 to about 0.4 wt %, or about 0.4 to about 0.5wt % SnO₂. In some embodiments, the glass or glass ceramic compositioncan comprise about 0, >0, 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5 wt % SnO₂.

In some embodiments, the sum of the weight percentage of P₂O₅ and ZrO₂in the glasses and glass ceramics disclosed herein can be greater thanor equal to about 3 wt %, 4 wt %, or 5 wt % to increase nucleation. Anincrease in nucleation can lead to the production of finer grains.

In some embodiments, the glass-ceramic exhibits transparency (i.e., theglass-ceramic is transparent) over the visible light range. In someembodiments, transparency of the glass-ceramic can be achieved byproducing crystals smaller than the wavelength of the interrogatingwavelength of light and by matching the index of refraction of theresidual glass with that of petatlite (1.51) and lithium disilicate(1.55). In some embodiments, the a transparent glass-ceramic having athickness of 1 mm can have a transmittance of 90% of light (includingsurface reflection losses) over the wavelength range from about 400 nmto about 1, 000 nm. In one or more embodiments, the averagetransmittance for a transparent glass-ceramic article is about 85% orgreater, about 86% or greater, about 87% or greater, about 88% orgreater, about 89% or greater, about 90% or greater, about 91% orgreater, about 92% or greater, about 93% or greater (including surfacereflection losses) of light over the wavelength range of about 400 nm toabout 1000 nm for a glass-ceramic article having a thickness of 1 mm. Inother embodiments, glass-ceramic may be translucent over the visiblelight range. In some embodiments a translucent glass-ceramic can have anaverage transmittance in a range from about 20% to less than about 85%of light over the wavelength range of about 400 nm to about 1000 nm fora glass-ceramic article having a thickness of 1 mm In embodiments wherethe glass-ceramic is translucent, the glass-ceramic can have a whitecolor.

In some embodiments, the size of the grains in the glass-ceramic mayaffect the transparency or translucency. In some embodiments, the grainsof transparent glass-ceramics may have a longest dimension of less thanabout 100 nm. In some embodiments, the grains of translucentglass-ceramics may have a longest dimension in a range from about 100 nmto about 500 nm. In some embodiments, the grains of transparentglass-ceramics may have an aspect ratio of about 2 or greater. In someembodiments, the grains of translucent glass-ceramics may have an aspectratio of about 2 or less.

As a result of the raw materials and/or equipment used to produce theglass or glass ceramic composition of the present disclosure, certainimpurities or components that are not intentionally added, can bepresent in the final glass or glass ceramic composition. Such materialsare present in the glass or glass ceramic composition in minor amountsand are referred to herein as “tramp materials.”

As used herein, a glass or glass ceramic composition having 0 wt % of acompound is defined as meaning that the compound, molecule, or elementwas not purposefully added to the composition, but the composition maystill comprise the compound, typically in tramp or trace amounts.Similarly, “iron-free, ” “sodium-free, ” “lithium-free, ”“zirconium-free, ” “alkali earth metal-free, ” “heavy metal-free” or thelike are defined to mean that the compound, molecule, or element was notpurposefully added to the composition, but the composition may stillcomprise iron, sodium, lithium, zirconium, alkali earth metals, or heavymetals, etc., but in approximately tramp or trace amounts. Trampcompounds that may be found in glass or glass ceramic embodied hereininclude, but are not limited to, Na₂O, TiO₂, MnO, ZnO, Nb₂O₅, MoO₃,Ta₂O₅, WO₃, ZrO₂, Y₂O₃, La₂O₃, HfO₂, CdO, SnO₂, Fe₂O₃, CeO₂, As₂O₃,Sb₂O₃, sulfur-based compounds, such as sulfates, halogens, orcombinations thereof.

In some embodiments, antimicrobial components may be added to the glassor glass ceramic composition. This is particularly advantageous as glassceramics embodied herein can be used in applications such as kitchen ordining countertops where exposure to harmful bacteria is likely.Antimicrobial components that may be added to the glass or glass ceramicinclude, but are not limited to, Ag, AgO, Cu, CuO, Cu₂O, and the like.In some embodiments, the concentrations of the antimicrobial componentsare kept at a level of about 3, 2, 1, or 0.5, >0 wt %. In someembodiments, the antimicrobial components is from >0 to about 3 wt %. Insome embodiments, the antimicrobial components is from >0 to about 1 wt%.

In some embodiments, the glass or glass ceramic may further include achemical fining agent. Such fining agents include, but are not limitedto, SnO₂, As₂O₃, Sb₂O₃, F, Cl and Br. In some embodiments, theconcentrations of the chemical fining agents are kept at a level of 3,2, 1, or 0.5, >0 wt %. In some embodiments, the fining agent amount isfrom >0 to about 3 wt %. Chemical fining agents may also include CeO₂,Fe₂O₃, and other oxides of transition metals, such as MnO₂. These oxidesmay introduce unwanted color to the glass or glass ceramic via visibleabsorptions in their final valence state(s) in the glass, and thus, whenpresent, their concentration is usually kept at a level of 0.5, 0.4,0.3, 0.2, 0.1 or >0 wt %.

The glasses or glass ceramics can also contain SnO2 either as a resultof Joule melting using tin-oxide electrodes, through the batching of tincontaining materials, e.g., SnO₂, SnO, SnCO₃, SnC₂O₂, etc., or throughaddition of SnO₂ as an agent to adjust various physical, melting, color,or forming attributes. The glass or glass ceramic can comprise from 0 toabout 3 wt %, 0 to about 2 wt %, 0 to about 1 wt %, 0 to 0.5 wt %, or 0to 0.1 wt % SnO₂.

In some embodiments, the glass or glass ceramic can be substantiallyfree of Sb₂O₃, As₂O₃, or combinations thereof. For example, the glass orglass ceramic can comprise 0.05 weight percent or less of Sb₂O₃ or As₂O₃or a combination thereof, the glass or glass ceramic may comprise 0 wt %of or As₂O₃ or a combination thereof, or the glass or glass ceramic maybe, for example, free of any intentionally added Sb₂O₃, As₂O₃, orcombinations thereof.

Additional components can be incorporated into the glass compositions toprovide additional benefits or alternatively, can further comprisecontaminants typically found in commercially-prepared glass. Forexample, additional components can be added to adjust various physical,melting, and forming attributes. The glasses, according to someembodiments, can also include various contaminants associated with batchmaterials and/or introduced into the glass by the melting, fining,and/or forming equipment used to produce the glass (e.g., ZrO₂). In someembodiments, the glass may comprise one or more compounds useful asultraviolet radiation absorbers. In some embodiments, the glass cancomprise 3 wt % or less TiO₂, MnO, ZnO, Nb₂O₅, MoO₃, Ta₂O₅, WO₃, ZrO₂,Y₂O₃, La₂O₃, HfO₂, CdO, Fe₂O₃, CeO₂, or combinations thereof. In someembodiments, the glass can comprise from 0 to about 3 wt %, 0 to about 2wt %, 0 to about 1 wt %, 0 to 0.5 wt %, 0 to 0.1 wt %, 0 to 0.05 wt %,or 0 to 0.01 wt % TiO₂, MnO, ZnO, Nb₂O₅, MoO₃, Ta₂O₅, WO₃, ZrO₂, Y₂O₃,La₂O₃, HfO₂, CdO, SnO₂, Fe₂O₃, CeO₂, As₂O₃, Sb₂O₃ or combinationsthereof.

In some embodiments, the glasses described herein can be manufacturedinto sheets via processes, including but not limited to, slot draw,float, rolling, and other sheet-forming processes known to those skilledin the art. Alternatively, glass compositions may be formed via float orrolling processes known in the art.

In some embodiments, the glass compositions described here may becompatible with float-type forming processes with an adjustment of theliquidus viscosity. In some embodiments, the glass composition can havea liquidus viscosity of from about 1500 P to about 3000 P. In someembodiments, the glass composition can have a liquidus viscosity ofabout 1000, 1200, 1500, 2000, 2500, or 3000 P.

In some embodiments, the glass can have a coefficient of thermalexpansion of about 50×10⁻⁷/K or greater, about 50×10⁻⁷/K or greater,about 60×10⁻⁷/K or greater, about 61×10⁻⁷/K or greater, about 62×10⁻⁷/Kor greater, about 63×10⁻⁷/K or greater, about 64×10⁻⁷/K or greater,about 65×10⁻⁷/K or greater, about 66×10⁻⁷/K or greater, about 67×10⁻⁷/Kor greater, about 68×10⁻⁷/K or greater, about 69×10⁻⁷/Kor greater, about70×10⁻⁷/K or greater, about 71×10⁻⁷/K or greater, about 72×10⁻⁷/K orgreater, about 73×10⁻⁷/K or greater, about 74×10⁻⁷/K or greater, about75×10⁻⁷/K or greater, about 76×10⁻⁷/K or greater, about 77×10⁻⁷/K orgreater, about 78×10⁻⁷/K or greater, about 79×10⁻⁷/K or greater, orabout 80×10⁻⁷/K or greater.

The articles formed from the glasses and glass ceramics described hereincan be any thickness that is reasonably useful. Glass sheet and/or glassceramic embodiments may have a thickness anywhere from about 0.8 mm toabout 10 mm. Some embodiments have thickness of about 6 mm or less,about 5 mm or less, about 3 mm or less, about 1.0 mm or less, about 750μm or less, about 500 μm or less, or about 250 μm or less. Some glass orglass ceramic sheet embodiments may have thickness of from about 200 μmto about 5 mm, about 500 μm to about 5 mm, about 200 μm to about 4 mm,about 200 μm to about 2 mm, about 400 μm to about 5 mm, or about 400 μmto about 2 mm. In some embodiments, the thickness may be from about 3 mmto about 6 mm or from about 0.8 mm to about 3 mm.

In some embodiments, the glass ceramic has an equibiaxial flexuralstrength of about 300 MPa or greater, about 325 MPa or greater, about350 MPa or greater, about 375 MPa or greater, about 400 MPa or greater,about 425 MPa or greater, or about 450 MPa or greater on a 1 mm thickglass-ceramic. The equibiaxial flexural strength can also be referred toas ring-on-ring (RoR) strength, which is measured according theprocedure set forth in ASTM: C1499-05, with a few modifications to testfixtures and test conditions as outlined in U.S. Patent Publication No.2013/0045375, at [0027], which is incorporated herein by reference. Anabraded ring-on-ring (aRoR) strength can also be measured using theprocedure described above if the glass-ceramic is first subjected toabrasion, typically with silicon carbide particles. Some embodimentsalso include a chemically-strengthenable glass ceramic with a petalitephase that leads to increased flexural strength. In such embodiments,the RoR strength may be about 500 MPa or greater, about 550 MPa orgreater, about 600 MPa or greater, about 650 MPa or greater, about 700MPa or greater, about 750 MPa or greater, or about 800 MPa or greater.

Some embodiments of the glass ceramics exhibit high fracture toughnessand an inherent damage resistance. As mentioned above, some embodimentsof the glass ceramic include interlocking lithium silicate crystals,which result in a high fracture toughness. The glass ceramic of one ormore embodiment may include boron, which may be present asthree-coordinated boron in the residual glass phase of the glassceramic. In such embodiments, the three-coordinated boron is provided bythe inclusion of B₂O₃ in the precursor glass. The three-coordinatedboron provides a densification mechanism when the glass or glass ceramicis subjected to an indentation load.

In one or more embodiments, the glass ceramics exhibit a fracturetoughness of about 1.0 MPa·m^(1/2) or greater, about 1.1 MPa·m^(1/2) orgreater, 1.2 MPa·m^(1/2) or greater, 1.3 MPa·m^(1/2) or greater, 1.4MPa·m^(1/2) or greater, 1.5 MPa·m^(1/2) or greater, 1.6 MPa·m^(1/2) orgreater, 1.7 MPa·m^(1/2) or greater, 1.8 MPa·m^(1/2) or greater, 1.9MPa·m^(1/2) or greater, or about 2.0 MPa·m^(1/2) In some embodiments,the fracture toughness is in the range from about 1 to about 2MPa·m^(1/2). The fracture toughness may be measured using known methodsin the art, for example, using a chevron notch short beam, according toASTM C1421-10, “Standard Test Methods for Determination of FractureToughness of Advanced Ceramics at Ambient Temperature”.

In one or more embodiments, the glass ceramics have high crack andscratch resistance by exhibiting a Vickers hardness. In someembodiments, a non-ion-exchanged glass ceramic exhibits a Vickershardness in the range from about 600 to about 900 kgf/mm², about 600 toabout 875 kgf/mm², about 600 to about 850 kgf/mm², about 600 to about825 kgf/mm², about 600 to about 800 kgf/mm², about 600 to about 775kgf/mm², about 600 to about 750 kgf/mm², about 600 to about 725 kgf/mm²,about 600 to about 700 kgf/mm², from about 700 to about 900 kgf/mm²,about 700 to about 875 kgf/mm², about 700 to about 850 kgf/mm², about700 to about 825 kgf/mm², or about 700 to about 800 kgf/mm². In someembodiments, a Vickers hardness is 600 kgf/mm² or greater, 625 kgf/mm²or greater, 650 kgf/mm² or greater, 675 kgf/mm² or greater, 700 kgf/mm²or greater, 725 kgf/mm² or greater, 750 kgf/mm² or greater, 775 kgf/mm²or greater, 800 kgf/mm² or greater, 825 kgf/mm² or greater, 850 kgf/mm²or greater, 875 kgf/mm² or greater, or 900 kgf/mm² or greater. Vickershardness may be measured using ASTM C1326 and C1327 (and its progeny,all herein incorporated by reference) “Standard Test Methods for VickersIndentation Hardness of Advanced Ceramics, ” ASTM International,Conshohocken, Pa., US. In some embodiments, the glass ceramics exhibitsuch Vickers indentation crack initiation load values after beingchemically strengthened via ion exchange.

In some embodiments, the glass ceramics disclosed herein are notfrangible upon being ion-exchanged. As used herein, the terms“frangible” and “frangibilty” refer to the energetic fracture of a glassceramic plate or sheet, when subjected to a point impact by an object ora drop onto a solid surface with sufficient force to break the glassceramic plate into multiple small pieces, with either multiple crackbranching (i.e.,

Attorney Docket No. SP14-291TBTA1D greater than 5 multiple cracksbranching from an initial crack) in the glass, ejection of pieces fromtheir original location of at least two inches (about 5 cm), afragmentation density of greater than about 5 fragments/cm² of theplate, or any combination of these three conditions. Conversely, a glassceramic plate is deemed to be not frangible if it either does not breakor breaks with less than five multiple cracks branching from an initialcrack with pieces ejected less than two inches from their originallocation when subjected to a point impact by an object or a drop onto asolid surface with sufficient force to break the glass ceramic plate.

Examples of frangible and non-frangible behavior observed for 5 cm x 5cm glass ceramic plates, each having a thickness of 0.5 mm, are shown inFIG. 10. Glass ceramic plate a exhibits frangible behavior, as evidencedby the multiple small pieces that have been ejected more than twoinches, and a large degree of crack branching from the initial crack toproduce the small pieces. In contrast to glass ceramic plate a, glassceramic plates b, c, and d do not exhibit frangible behavior. In theseinstances, the glass ceramic plate breaks into a small number of largepieces that are not forcefully ejected 2 inches from their originallocation (“X” is the approximate center of glass plate a beforefracture). Glass ceramic plate b has broken into two large pieces withno crack branching; glass ceramic plate c has broken into four pieceswith two cracks branching from the initial crack; and glass ceramicplate d has broken into four pieces with two cracks branching from theinitial crack.

In addition, all of the compositions and glasses and/or glass ceramicscompositions are ion exchangeable by those methods widely known in theart. In typical ion exchange processes, smaller metal ions in the glassare replaced or “exchanged” by larger metal ions of the same valencewithin a layer that is close to the outer surface of the glass and/orglass ceramic. The replacement of smaller ions with larger ions createsa compressive stress within the layer of the glass and/or glass ceramic.In one embodiment, the metal ions are monovalent alkali metal ions(e.g., Na+, K+, Rb+, Cs+and the like), and ion exchange is accomplishedby immersing the glass and/or glass ceramic in a bath comprising atleast one molten salt of the larger metal ion that is to replace thesmaller metal ion in the glass. Alternatively, other monovalent ionssuch as Ag⁺, Tl⁺, Cu⁺, and the like may be exchanged for monovalentions. The ion exchange process or processes that are used to strengthenthe glass and/or glass ceramic can include, but are not limited to,immersion in a single bath or multiple baths of like or differentcompositions with washing and/or annealing steps between immersions. Inone or more embodiments, the glasses and/or glass-ceramics may be ionexchanged by exposure to molten NaNO₃ at a temperature of about 430° C.. In such embodiments, the Na+ ions replace some portion of the Li ionsin the glass ceramic to develop a surface compressive layer and exhibithigh crack resistance. The resulting compressive stress layer may have adepth (also referred to as a “depth of layer”) of at least 100 μm on thesurface of the glass in about 2 hours. In such embodiments, thedepth-of-layer can be determined from the Na₂O concentration profile. Inother examples, embodiments may be ion exchanged by exposure to moltenKNOB at a temperature of 410° C. for 2 hours to produce a compressivestress layer having a depth of layer of at least about 100 μm. In someembodiments, the glass-ceramics may be ion exchanged to achieve a depthof layer of about 30 μm or greater, about 40 μm or greater, about 50 μmor greater, about 60 μm or greater, about 70 μm or greater, about 80 μmor greater, about 90 μm or greater, or about 100 μm or greater. In otherembodiments the glasses are ion exchanged to achieve a central tensionof at least 10 MPa. The development of this surface compression layer isbeneficial for achieving a better crack resistance and higher flexuralstrength compared to non-ion-exchanged materials. The surfacecompression layer has a higher concentration of the ion exchanged intothe glass-ceramic article in comparison to the concentration of the ionexchanged into the glass-ceramic article for the body (i.e., area notincluding the surface compression) of the glass-ceramic article.

In some embodiments, the glass-ceramic can have a surface compressivestress in a range from about 100 MPa to about 500 MPa, about 100 MPa toabout 450 MPa, about 100 MPa to about 400 MPa, about 100 MPa to about350 MPa, about 100 MPa to about 300 MPa, about 100 MPa to about 250 MPa,about 100 MPa to about 200 MPa, about 100 MPa to about 150 MPa, 150 MPato about 500 MPa, about 150 MPa to about 450 MPa, about 150 MPa to about400 MPa, about 150 MPa to about 350 MPa, about 150 MPa to about 300 MPa,about 150 MPa to about 250 MPa, about 150 MPa to about 200 MPa, 200 MPato about 500 MPa, about 200 MPa to about 450 MPa, about 200 MPa to about400 MPa, about 200 MPa to about 350 MPa, about 200 MPa to about 300 MPa,about 200 MPa to about 250 MPa, 250 MPa to about 500 MPa, about 250 MPato about 450 MPa, about 250 MPa to about 400 MPa, about 250 MPa to about350 MPa, about 250 MPa to about 300 MPa, 300 MPa to about 500 MPa, about300 MPa to about 450 MPa, about 300 MPa to about 400 MPa, about 300 MPato about 350 MPa, 350 MPa to about 500 MPa, about 350 MPa to about 450MPa, about 350 MPa to about 400 MPa, 400 MPa to about 500 MPa, about 400MPa to about 450 MPa, or about 450 MPa to about 500 MPa. In someembodiments, the glass-ceramic can have a surface compressive stress ofabout 100 MPa or greater, about 150 MPa or greater, about 200 MPa orgreater, about 250 MPa or greater, about 300 MPa or greater, about 350MPa or greater, about 400 MPa or greater, about 450 MPa or greater, orabout 500 MPa or greater. Compressive stress and depth of compressivestress layer (“DOL”) are measured using those means known in the art.DOL is determined by surface stress meter (FSM) using commerciallyavailable instruments such as the FSM-6000, manufactured by Luceo Co.,Ltd. (Tokyo, Japan), or the like, and methods of measuring CS and depthof layer are described in ASTM 1422C-99, entitled “StandardSpecification for Chemically Strengthened Flat Glass, ” and ASTM1279.19779 “Standard Test Method for Non-Destructive PhotoelasticMeasurement of Edge and Surface Stresses in Annealed, Heat-Strengthened,and Fully-Tempered Flat Glass, ” the contents of which are incorporatedherein by reference in their entirety. Surface stress measurements relyupon the accurate measurement of the stress optical coefficient (SOC),which is related to the birefringence of the glass. SOC in turn ismeasured by those methods that are known in the art, such as fiber andfour point bend methods, both of which are described in ASTM standardC770-98 (2008), entitled “Standard Test Method for Measurement of GlassStress-Optical Coefficient, ” the contents of which are incorporatedherein by reference in their entirety, and a bulk cylinder method.

In one or more embodiments, the processes for making the glass ceramicincludes heat treating the precursor glasses at one or more preselectedtemperatures for one or more preselected times to induce glasshomogenization and crystallization (i.e., nucleation and growth) of oneor more crystalline phases (e.g., having one or more compositions,amounts, morphologies, sizes or size distributions, etc.). In someembodiments, the heat treatment can include (i) heating precursorglasses at a rate of 1-10° C./min to a glass pre-nucleation temperature:(ii) maintaining the crystallizable glasses at the glass pre-nucleationtemperature for a time in a range from about ¼ hr to about 4 hr toproduce pre-nucleated crystallizable glasses; (iii) heating thepre-nucleated crystallizable glasses at a rate of 1-10° C./min tonucleation temperature (Tn); (iv) maintaining the crystallizable glassesat the nucleation temperature for a time in the range from between about¼ hr to about 4 hr to produce nucleated crystallizable glasses; (v)heating the nucleated crystallizable glasses at a rate in the range fromabout 1° C./min to about 10 ° C./min to a crystallization temperature(Tc); (vi) maintaining the nucleated crystallizable glasses at thecrystallization temperature for a time in the range from about ¼ hr toabout 4 hr to produce the glass ceramic described herein; and (vii)cooling the formed glass ceramic to room temperature. As used herein,the term crystallization temperature may be used interchangeably withceram or ceramming temperature. In addition, the terms “ceram” or“ceramming” in these embodiments, may be used to refer to steps (v),(vi) and optionally (vii), collectively. In some embodiments, the glasspre-nucleation temperature can be 540° C., the nucleation temperaturecan be 600° C., and the crystallization temperature can be in a rangefrom 630° C. to 730° C. In other embodiments, the heat treatment doesnot include maintaining the crystallizable glasses at a glasspre-nucleation temperature. Thus the can heat treatment may include (i)heating precursor glasses at a rate of 1-10° C./min to a nucleationtemperature (Tn); (ii) maintaining the crystallizable glasses at thenucleation temperature for a time in the range from between about ¼ hrto about 4 hr to produce nucleated crystallizable glasses; (iii) heatingthe nucleated crystallizable glasses at a rate in the range from about1° C./min to about 10 ° C./min to a crystallization temperature (Tc);(iv) maintaining the nucleated crystallizable glasses at thecrystallization temperature for a time in the range from about ¼ hr toabout 4 hr to produce the glass ceramic described herein; and (v)cooling the formed glass ceramic to room temperature. The terms “ceram”or “ceramming”, in the preceding embodiments, may be used to refer tosteps (iii), (iv) and optionally (v), collectively. In some embodiments,the nucleation temperature can be about 700° C., and the crystallizationtemperature can be about 800° C. In some embodiments, the higher thecrystallization temperature, the more β-spodumene ss is produced as aminor crystalline phase.

Temperature-temporal profile of heat treatment steps of heating to thecrystallization temperature and maintaining the temperature at thecrystallization temperature in addition to precursor glass compositions,are judiciously prescribed so as to produce one or more of the followingdesired attributes: crystalline phase(s) of the glass ceramic,proportions of one or more major crystalline phases and/or one or moreminor crystalline phases and residual glass, crystal phase assemblagesof one or more predominate crystalline phases and/or one or more minorcrystalline phases and residual glass, and grain sizes or grain sizedistributions among one or more major crystalline phases and/or one ormore minor crystalline phases, which in turn may influence the finalintegrity, quality, color, and/or opacity, of resultant formed glassceramic.

The resultant glass ceramic can be provided as a sheet, which can thenbe reformed by pressing, blowing, bending, sagging, vacuum forming, orother means into curved or bent pieces of uniform thickness. Reformingcan be done before thermally treating or the forming step can also serveas a thermal treatment step where both forming and thermally treatingare performed substantially simultaneously.

In yet other embodiments, the precursor glass compositions used to formthe glass ceramic can be formulated, for example, so that the glassceramic is capable of being chemically strengthened using one or moreion exchange techniques. In these embodiments, ion exchange can occur bysubjecting one or more surfaces of such glass ceramic to one or more ionexchange baths, having a specific composition and temperature, for aspecified time period to impart to the one or more surfaces withcompressive stress layer(s). The compressive stress layer can includeone or more average surface compressive stress (CS), and/or one or moredepths of layer.

EXAMPLES

Efforts have been made to ensure accuracy with respect to numbers (e.g.,amounts, temperature, etc.) but some errors and deviations should beaccounted for.

Unless indicated otherwise, temperature is in ° C or is at ambienttemperature, and pressure is at or near atmospheric. The compositionsthemselves are given in wt % on an oxide basis and have been normalizedto 100%. There are numerous variations and combinations of reactionconditions, e.g., component concentrations, temperatures, pressures andother reaction ranges and conditions that can be used to optimize theproduct purity and yield obtained from the described process. Onlyreasonable and routine experimentation will be required to optimize suchprocess conditions.

Example 1

Example glass and glass ceramic compositions (in terms of wt %) andproperties for achieving transparent glass ceramics are set forth in theTable 1 and were determined in accordance with techniques conventionalin the glass art. Precursor glasses were formed having the compositions1-16 listed in Table 1. The precursor glasses were then subjected to aceramming cycle having a glass homogenization hold at 540° C. for 4hours, a nucleation hold at 600° C. for 4 hours, and a crystallizationhold at a temperature in a range from 630 to 730° C. for 4 hours. Thefollowing nomenclature was used in Table 1 to describe the cerammingcycle: glass homogenization temperature—hold time/nucleationtemperature—hold time/crystallization temperature—hold time.

The liquidus temperature is the temperature where the first crystal isobserved in a standard gradient boat liquidus measurement (ASTM C829-81and it progeny). This involves placing crushed glass particles in aplatinum boat, placing the boat in a furnace having a region of gradienttemperatures, heating the boat in an appropriate temperature region for24 or 72 hours, and determining by means of microscopic examination thehighest temperature at which crystals appear in the interior of theglass. More particularly, the glass sample is removed from the Pt boatin one piece, and examined using polarized light microscopy to identifythe location and nature of crystals which have formed against the Pt andair interfaces, and in the interior of the sample. Because the gradientof the furnace is very well known, temperature vs. location can be wellestimated, within 5-10° C. The temperature at which crystals areobserved in the internal portion of the sample is taken to represent theliquidus of the glass (for the corresponding test period). Testing issometimes carried out at longer times (e.g. 72 hours), in order toobserve slower growing phases. The liquidus viscosity in poises wasdetermined from the liquidus temperature and the coefficients of theFulcher equation.

TABLE 1 Composition 1 2 3 4 5 6 7 8 SiO₂ (wt %) 78.3 78.3 78.3 78.3 78.378.3 78.3 78.3 Al₂O₃ (wt %) 7.5 8.1 8.7 8.1 8.1 8.1 8.1 8.1 B₂O₃ (wt %)0.0 0.2 0.4 1.0 2.0 4.0 5.0 6.0 Li₂O (wt %) 12.5 11.9 11.3 11.9 11.911.9 11.9 11.9 Na₂O (wt %) 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 K₂O (wt %)0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 ZnO (wt %) 0.0 0.0 0.0 0.0 0.0 0.0 0.00.0 ZrO₂ (wt %) 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 P₂O₅ (wt %) 2.0 2.2 2.42.2 2.2 2.2 2.2 2.2 Ceramming 540° C.- 540° C.- 540° C.- 540° C.- 540°C.- 540° C.- 540° C.- 540° C.- cycle 4 hr/ 4 hr/ 4 hr/ 4 hr/ 4 hr/ 4 hr/4 hr/ 4 hr/ 600° C.- 600° C.- 600° C.- 600° C.- 600° C.- 600° C.- 600°C.- 600° C.- 4 hr/ 4 hr/ 4 hr/ 4 hr/ 4 hr/ 4 hr/ 4 hr/ 4 hr/ 730° C.-710° C.- 730° C.- 690° C.- 650° C.- 630° C.- 630° C.- 630° C.- 4 hr 4 hr4 hr 4 hr 4 hr 4 hr 4 hr 4 hr Phase Petalite, Petalite, Petalite,Petalite, Petalite, Petalite, Petalite, Petalite, assemblage lithiumlithium lithium lithium lithium lithium lithium lithium disilicatedisilicate disilicate disilicate disilicate disilicate disilicatedisilicate Appearance Slight Clear, Slight Clear, Clear, Slight SlightSlight hazy, transparent hazy, transparent transparent hazy, hazy, hazy,transparent transparent transparent transparent transparent Liquidus1030 1050 1070 — — — — — temperature (° C.) Liquidus 3700 3800 3800 — —— — — viscosity (poise) Composition 9 10 11 12 13 14 15 16 SiO₂ (wt %)76.3 74.3 72.3 70.3 78.3 78.3 78.3 78.3 Al₂O₃ (wt %) 10.1 12.1 14.1 16.18.1 8.1 8.1 8.1 B₂O₃ (wt %) 0.2 0.2 0.2 0.2 2.0 2.0 2.0 2.0 Li₂O (wt %)11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 Na₂O (wt %) 1.7 1.7 1.7 1.7 0.00.0 0.0 0.0 K₂O (wt %) 0.0 0.0 0.0 0.0 1.5 3.0 0.0 0.0 ZnO (wt %) 0.00.0 0.0 0.0 0.0 0.0 1.5 3.0 ZrO₂ (wt %) 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0P₂O₅ (wt %) 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 Ceramming 540° C.- 540° C.-540° C.- 540° C.- 540° C.- 540° C.- 540° C.- 540° C.- cycle 4 hr/ 4 hr/4 hr/ 4 hr/ 4 hr/ 4 hr/ 4 hr/ 4 hr/ 600° C.- 600° C.- 600° C.- 600° C.-600° C.- 600° C.- 600° C.- 600° C.- 4 hr/ 4 hr/ 4 hr/ 4 hr/ 4 hr/ 4 hr/4 hr/ 4 hr/ 710° C.- 710° C.- 710° C.- 710° C.- 690° C.- 690° C.- 690°C.- 690° C.- 4 hr 4 hr 4 hr 4 hr 4 hr 4 hr 4 hr 4 hr Phase Petalite,Petalite, Petalite, Petalite, Petalite, Petalite, Petalite, Petalite,assemblage lithium lithium lithium lithium lithium lithium lithiumlithium disilicate disilicate disilicate disilicate disilicatedisilicate disilicate disilicate Appearance Slight Hazy, TranslucentTranslucent Clear, Slight Slight Translucent haze, transparent whitecreamy transparent hazy, hazy, white transparent white transparenttranspaentr Liquidus — — — — — — — — temperature (° C.) Liquidus — — — —— — — — viscosity (poise)

Several tests were done on Composition 2 after ceramming to determine avariety of properties for the glass-ceramic of Composition 2. As shownin FIG. 1, a differential scanning calorimetry (DSC) trace was performedfor Composition 2 plotting DSC/(mW/mg) vs. temperature in degreesCelsius. The trace was used to show that a fine-grained microstructurecan be achieved by ceramming at low temperatures relative tocrystallization temperatures.

The transmittance of glass-ceramic composition 2 having a thickness of 1mm was measured for light having a wavelength from 400 nm to 1, 000 nm.As shown in FIG. 2, the average transmittance of glass-ceramiccomposition 2 in the visible light wavelength is greater than 90%.

A sample of glass-ceramic composition 2 was observed using a scanningelectron microscope (SEM) to determine the grain size of the petalite.FIG. 3A shows the SEM on a 200 nm scale and FIG. 3B shows the SEM on a100 nm scale. The petalite grains are on the order of 50 to 100 nm. Thefineness of the grains is believed to contribute to the transparency ofthe glass-ceramic evidenced in FIG. 2.

Two 50 mm by 50 mm by 1 mm samples of glass-ceramic composition 2 weresubjected to a ring-on-ring test as described above to determine thestrength of the samples. One sample had been subjected to abrasion (15psi) and one sample was not. FIG. 4 shows the results of thering-on-ring test. A strength of 514 MPa was achieved for thering-on-ring test.

The fracture toughness of a sample of glass-ceramic composition 2 wasmeasured using chevron notched short beam measurements. The fracturetoughness was 1.13 MPa·m1/2.

The hardness of a sample of glass-ceramic composition was measured todetermine the Vickers hardness as described above using a Model 5948MicroTester, available from Instron. The Vickers hardness wasapproximately 750 kgf/mm².

A glass-ceramic of composition 2 was subjected to an ion-exchangeprocess wherein the sample was placed in a molten NaNO3 bath at 430° C.for 2 hours, 4 hours, 8 hours, and 16 hours. As shown in FIG. 5, a depthof layer of over 100 μm was achieved. FIG. 5 also shows a plot of theconcentration of Na₂O in mole percent vs. thickness of the sample foreach ion-exchange treatment. As can be seen, the depth of layerincreased with increasing duration of the ion-exchange treatment. Also,a parabolic Na₂O concentration was achieved after ion-exchanging for 16hours.

Two 50 mm by 50 mm by 1 mm samples glass-ceramic of composition 2 wereion-exchanged. One sample was ion-exchanged in a molten NaNO3 bath at430° C. for 2 hours and the other sample was ion-exchanged in a moltenKNO3 bath at 430° C. for 2 hours. The two ion-exchanged samples and anon-ion-exchanged 50 mm by 50 mm by 1 mm sample of glass-ceramic ofcomposition 2 were subjected to a ring-on-ring test as described above.The results are shown in FIG. 6. The strength of the glass-ceramic hadapproximately a 30% increase after ion-exchanging with NaNO3 andapproximately doubled after ion-exchanging with KNO₃. It is believedthat ion-exchanging with a KNO3 bath results in a greater depth-of-layer(DOL) for the compressive stress layer formed on the surface of thesample during ion exchange.

A 50 mm by 50 mm by 1mm sample of glass-ceramic of composition 2 wasion-exchanged in a molten NaNO3 bath at 430° C. for 2 hours. A 50 mm by50 mm by 1 mm sample of glass A was ion-exchanged in a molten KNO3 bathat 420° C. for 5.5 hours. A 50 mm by 50 mm by 1 mm sample of glass B wasion-exchanged in a 32% KNO3 molten bath at 540° C. for 8 hours followedby ion-exchanging in a 100% KNO3 molten bath at 390° C. for 15 mins. Thesamples were all abraded under 15 psi and subjected to an abradedring-on-ring test as described above. The results are shown in FIG. 7.The glass-ceramic had a higher strength than glass A and had a strengthapproaching that of glass B. Thus the ion-exchanged glass ceramics canbe just as strong or stronger than ion-exchanged glass.

50 mm by 50mm by 1mm samples of glass-ceramic of composition 2 wereion-exchanged in a molten NaNO3 bath at 430° C. for 2 hours, 4 hours, 8hours, and 16 hours. The ion-exchanged samples were then subjected to aring-on-ring test as described above as well as a non-ion-exchangedglass-ceramic sample of composition 2. The results are shown in FIG. 8.The strength of the glass-ceramic increased based on the duration of theion-exchange.

50 mm by 50 mm by 1mm samples of glass-ceramic of composition 2 wereion-exchanged in a molten NaNO3 bath at 430° C. for 16 hours. Thesamples were abraded under 15 psi, 25 psi, or 45 psi and subjected to anabraded ring-on-ring test as described above. The results are shown inFIG. 9. The samples abraded under 15 psi had a load failure of about 253MPa, the samples abraded under 25 psi had a load failure of about 240MPa, and the samples abraded under 45 psi had a load failure of about201 MPa.

Example 2

Example glass and glass ceramic compositions (in terms of wt %) andproperties for achieving translucent glass ceramics are set forth in theTable 2 and were determined in accordance with techniques conventionalin the glass art. Precursor glasses were formed having the compositions17-29 listed in Table 2. The precursor glasses were then subjected to aceramming cycle indicated in Table 2 below.

TABLE 2 Composition 17 18 19 20 21 22 23 SiO₂ (wt %) 78.3 78.3 78.3 78.378.3 78.3 76.3 Al₂O₃ (wt %) 10.5 9.3 9.3 9.3 7.5 8.1 8.7 B₂O₃ (wt %) 10.6 0.6 0.6 0.0 0.2 0.4 Li₂O (wt %) 9.5 10.7 10.7 10.7 12.5 11.9 11.3Na₂O (wt %) 1.7 1.7 1.7 1.7 1.7 1.7 1.7 K₂O (wt %) 0.0 0.0 0.0 0.0 0.00.0 0.0 ZnO (wt %) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 ZrO₂ (wt %) 4.0 4.0 6.08.0 4.0 4.0 4.0 P₂O₅ (wt %) 3.0 2.0 2.0 2.0 2.0 2.2 2.4 Ceramming 700°C.- 700° C.- 700° C.- 700° C.- 540° C.- 540° C.- 540° C.- cycle 0.5 hr/0.5 hr/ 0.5 hr/ 0.5 hr/ 4 hr/ 4 hr/ 4 hr/ 800° C.- 800° C.- 800° C.-800° C.- 600° C.- 600° C.- 600° C.- 0.5 hr 0.5 hr 0.5 hr 0.5 hr 4 hr/ 4hr/ 4 hr/ 730° C.- 740° C.- 730° C.- 4 hr 4 hr 4 hr Phase Petalite,Petalite, Petalite, Petalite, Petalite, Petalite, Petalite, assemblagelithium lithium lithium lithium lithium lithium lithium disilicate,disilicate, disilicate, disilicate, disilicate disilicate, disilicatelithiophosphate lithiophosphate β-quartz cristobalite, β-quartzlithiophosphate lithiophosphate Appearance Translucent TranslucentTranslucent Translucent Slight Transparent Slight white white whitewhite hazy, hazy, transparent transparent Liquidus 1070 1060 1055 12201030 1050 1070 temperature (° C.) Liquidus 9800 5900 6100 880 3700 38003800 viscosity (poise) Composition 24 25 26 27 28 29 SiO₂ (wt %) 72.378.3 78.3 78.3 78.3 78.3 Al₂O₃ (wt %) 14.1 10.5 8.1 10.1 11.1 12.1 B₂O₃(wt %) 0.2 1 0.2 0.2 0.2 0.2 Li₂O (wt %) 11.9 9.5 11.9 11.9 11.9 11.9Na₂O (wt %) 1.7 0 0 0 0 0 K₂O (wt %) 0.0 1.7 1.7 1.7 1.7 1.7 ZnO (wt %)0.0 0 0 0 0 0 ZrO₂ (wt %) 4.0 4 4 4 4 4 P₂O₅ (wt %) 2.2 3 2.2 2.2 2.22.2 Ceramming 540° C.-4 hr/ 540° C.-4 hr/ 540° C.-4 hr/ 540° C.-4 hr/540° C.-4 hr/ 540° C.-4 hr/ cycle 600° C.-4 hr/ 600° C.-4 hr/ 600° C.-4hr/ 600° C.-4 hr/ 600° C.-4 hr/ 600° C.-4 hr/ 630° C.-4 hr 680° C.-2 hr680° C.-2 hr 680° C.-2 hr 680° C.-2 hr 680° C.-2 hr Phase β-quartz, — —— — — assemblage petalite, lithium metasilicate Appearance TranslucentTranslucent Transparent Transparent Slightly Slightly white white hazy,hazy, transparent transparent Liquidus — — — — — — temperature (° C.)Liquidus — — — — — — viscosity (poise)

The fracture toughness of a sample of glass-ceramic Composition 17, 18,and 22 were measured using chevron notched short beam measurements. Thefracture toughness was 1.2 MPa·m^(1/2), 1.13 MPa·m^(1/2), and 1.2MPa·m^(1/2), respectively.

As shown in FIG. 11, a differential scanning calorimetry (DSC) trace wasperformed for Composition 18 plotting DSC/(mW/mg) vs. temperature indegrees Celsius. FIG. 12, is an X-ray diffraction (XRD) spectra of thecrystalline phases formed in Composition 18. It can be seen from the XRDspectra that petalite and lithium disilicate are the major crystallinephases.

50 mm by 50 mm by 1 mm samples of glass-ceramic Compositions 19, 20, and21 were subjected to a ring-on-ring test as described above to determinethe strength of the samples. FIG. 13 shows the results of thering-on-ring test. A strength of 352 MPa, 304 MPa, and 313 MPa wasachieved for the ring-on-ring test respectively. Thus, a strength ofover 300 MPa can be achieved for the translucent glass ceramicsdisclosed herein.

A glass-ceramic of composition 18 formed by batching a Na₂Oconcentration of 1.4 mol% into the bulk glass was subjected to anion-exchange process wherein the sample was placed in a molten NaNO3bath at 430° C. for 4hours. As shown in FIG. 14, a depth of layer ofover 100 μm was achieved. FIG. 14 also shows a plot of the concentrationof Na₂O in weight percent vs. thickness of the sample.

While embodiments and examples have been set forth for the purpose ofillustration, the foregoing description should not be deemed to be alimitation on the scope of the disclosure or appended claims.Accordingly, various modifications, adaptations, and alternatives mayoccur to one skilled in the art without departing from the spirit andscope of the present disclosure or appended claims.

1. A lithium-containing aluminosilicate glass-ceramic articlecomprising: a fracture toughness of 1 MPa·m^(1/2) or greater; aring-on-ring strength of at least 300 MPa; a compressive stress layerformed by ion-exchange having a depth of layer (DOL) of at least about30 μm; and a transmittance of at least 85% for light in a wavelengthrange from 400 nm to 700 nm at a thickness of 1 mm, wherein the articleis not frangible.
 2. The article of claim 1, further comprising amicrostructure of randomly-oriented interlocked crystals.
 3. The articleof claim 2, wherein the randomly-oriented interlocked crystals areorthorhombic.
 4. The article of claim 2, wherein the randomly-orientedinterlocked crystals comprise a tabular shape.
 5. The article of claim2, wherein the randomly-oriented interlocked crystals comprise alath-like shape.
 6. The article of claim 2, wherein randomly-orientedinterlocked crystals comprise lithium silicate.
 7. The article of claim6, wherein the lithium silicate comprises 20 to 60 wt % of the article.8. The article of claim 7, wherein the lithium silicate is a lithiumdisilicate crystalline phase.
 9. The article of claim 7, wherein thelithium silicate is a lithium metasilicate crystalline phase.
 10. Thearticle of claim 1, further comprising a microstructure of fine-grainedcrystals having a longest dimension of 100 nm or less.
 11. The articleof claim 10, wherein the fine-grained crystals are monoclinic.
 12. Thearticle of claim 10, wherein the fine-grained crystals comprise athree-dimensional layered framework.
 13. The article of claim 10,wherein the fine-grained crystals are petalite.
 14. The article of 13,wherein the petalite comprises 20 to 70 wt % of the article.
 15. Thearticle of claim 1, further comprising a surface compressive stress ofabout 100 MPa or greater.
 16. The article of claim 1, further comprisinga central tension of 10 MPa or more.
 17. The article of claim 1, furthercomprising a thickness from 200 micrometers to 2 mm.
 18. The article ofclaim 1, further comprising, in wt %: Na₂O: 0-5%; K₂O: 0-4%; B₂O₃:0-10%; P₂O₅: 0.5-6%; and ZrO₂: 0.2-15%.
 19. The article of claim 18,wherein: Na₂O from 0-2%; K₂O from 0-2%; P₂O₅ from 1.5-2.5%; and ZrO₂from 2-4%.
 20. The article of claim 18, wherein the sum of the weightpercentage of P₂O₅ and ZrO₂ is greater than or equal to 4 wt %.
 21. Thearticle of claim 1, further comprising: Li₂O in an amount of 5-20 wt %;SiO₂ in an amount of 55-80 wt %; Al₂O₃ in an amount of 2-20 wt %. 22.The article of claim 21, further comprising, Li₂O in an amount of 5-14wt %; SiO₂ in an amount of 69-80 wt %; Al₂O₃ in an amount of 2-9 wt %.23. The article of claim 1, further comprising a Vickers hardness ofabout 600 kgf /mm² or greater.
 24. The article of claim 1, furthercomprising a transmittance of at least 88% for light in a wavelengthrange from 400 nm to 700 nm at a thickness of 1 mm.
 25. An electronicdevice comprising a cover wherein the cover comprises the article ofclaim 1.